Fresh tissues, cultured cells, and nucleic acids will be obtained from Japanese and other Asiatic rodents and primates. After preliminary characterization, these materials will be sent to NCI in Bethesda, Md., for program distribution. Japanese primate tissues will be obtained principally from the several primate centers in operation in Japan. The wild rodents will be collected and maintained at the Laboratory of Genetics, National Institute of Genetics in Japan. Cultured cells, nucleic acid preparations, etc., will be obtained from representative organs of the test animals at the laboratory of the principal investigator. The collaborative procurement and studies in Japan and the USA will be performed to further clarify the phylegenetic aspects of endogenous type C viruses and other viruses among rodents and the relationship of such viruses to known oncogenic RNA tumor viruses, especially those isolated from nonhuman primates.